Note that the usual setup would be: SSD + DVD on Intel SATA III and HDD on Marvel SATA III. JMicron controller is disabled. Not using the Intel SATA II ports because of the sandy bridge chipset design flaw (damn you Intel!). For all following tests, I'm using setup (A).

4) Tried switching from AHCI to IDE, still get the same error.

5) Both HDD and SSD are completely clean and have never been used, formatted or anything before (just bought them new).

6) My saving grace, possibly! It seems that the CRC32 and SHA1 for my (already once redownloaded) ISO are NOT correct!

The website linked states that it should be:
Windows 7 Professional 64-bit:
Name: en_windows_7_professional_x64_dvd_x15-65805.iso
SHA-1: 50127304441A793EE51B3F501289F6599A559E9F
CRC: 502C42C1